So I have found sufficient information of mating the datalogger and the Ethenet shield and posting sensor data to the web for retrieval etc etc etc.
One thing I do not know, is it possible to set a loop where it logs for 24 hrs, posts the data, possibly an email? and then erases the card to continue logging for the next day.
All my experience with arduino's is with motors, sensors, and lcds. Using the web with it is something I have not yet touched on so any insight is greatly appreciated.
One thing I do not know, is it possible to set a loop where it logs for 24 hrs, posts the data, possibly an email? and then erases the card to continue logging for the next day.
I don't see any reason why not.
If you can log the data today, you should be able to create a new log file each day (provided you have a real time clock or other means of knowing when a new day starts).
If you can post the sensor data today, you should be able to post that data only once a day, when the day changes. Again, you need a way of knowing when the day changes.
You also need, obviously, to post a lot more data (that you have read from the SD card).
Which route do you think is best to go for this, Basically I wanna use 2 temperature sensors, 1 up stairs and 1 downstairs and prox switch on a door. Take measurements every 2 seconds, for 24 hrs, post then delete, restart. How hard is it set a real time clock in arduino?
How hard is it set a real time clock in arduino?
The millis() timeer overflows regularly (about every 47 days, iirc), so you have to watch out for that if you use it.
For my weather station, I used the DateTime library, which maintains a Unix-style clock. I POST readings to a PHP-based server every 2 minutes, and have the server send back its system time as part of the response. That ensures that the Arduino keeps a time that is "close enough" to correct (within the fraction of a second it takes to create, transmit, and decode the reply), and eliminates the need to attach something like a DS1307 to the Arduino or write my own code to handle millis()-to-TOD conversion.
Unless you specifically want to tackle the challenge of storing a whole day's data for batching, I'd recommend sending it more often. Keep in mind that the Arduino's Ethernet interface is pretty slow, and sending a big batch is likely to take longer than one of your 2-second reading cycles. You'll need to design your software accordingly.
Check - Data-Logger Shield for Arduino
It has almost all you need